Quantitative Proteomic Analysis of the Adipocyte Plasma Membrane

Prior, Matthew J.; Larance, Mark; Lawrence, Robert; Soul, Jamie; Humphrey, Sean J.; Burchfield, James G.; Kistler, Carol; Davey, Jonathon R; La-Borde, Penelope J.; Buckley, Michael; Kanazawa, Hiroshi; Parton, Robert G.; Guilhaus, Michael; James, David E.

doi:10.1021/pr200446r

Cited by 26 publications

(32 citation statements)

References 54 publications

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“…NHE6 has been shown to be translocated to the plasma membrane in adipocytes upon insulin stimulation, or in osteoblasts during bone mineralization6263. However, the detailed mechanisms responsible for the trafficking of NHE6 are not yet understood.…”

Section: Discussionmentioning

confidence: 99%

Hypoxia-induced mobilization of NHE6 to the plasma membrane triggers endosome hyperacidification and chemoresistance

et al. 2017

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The pH-dependent partitioning of chemotherapeutic drugs is a fundamental yet understudied drug distribution mechanism that may underlie the low success rates of current approaches to counter multidrug resistance (MDR). This mechanism is influenced by the hypoxic tumour microenvironment and results in selective trapping of weakly basic drugs into acidified compartments such as the extracellular environment. Here we report that hypoxia not only leads to acidification of the tumour microenvironment but also induces endosome hyperacidification. The acidity of the vesicular lumen, together with the alkaline pH of the cytoplasm, gives rise to a strong intracellular pH gradient that drives intravesicular drug trapping and chemoresistance. Endosome hyperacidification is due to the relocalization of the Na+/H+ exchanger isoform 6 (NHE6) from endosomes to the plasma membrane, an event that involves binding of NHE6 to the activated protein kinase C–receptor for activated C kinase 1 complex. These findings reveal a novel mechanism of hypoxia-induced MDR that involves the aberrant intracellular distribution of NHE6.

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Section: Discussionmentioning

confidence: 99%

Hypoxia-induced mobilization of NHE6 to the plasma membrane triggers endosome hyperacidification and chemoresistance

et al. 2017

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“…Metformin reduces oxygen consumption, and reduces autophagosome formation during long-term starvation, suggesting a connection between mitochondria and the endocytic cycle. NHE6, the homolog of C. elegans NHX-5, was identified as a novel insulin-responsive gene, suggesting that the trafficking of NHE6-loaded endosomes by insulin could play an important role in glucose homeostasis (29). It is possible that metformin could regulate NHE6 function so as to restore insulin sensitivity.…”

Section: Discussionmentioning

confidence: 99%

NHX-5, an Endosomal Na+/H+ Exchanger, Is Associated with Metformin Action

Kim

Lee

Ahn

et al. 2016

Journal of Biological Chemistry

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Diabetes is one of the most impactful diseases worldwide. The most commonly prescribed anti-diabetic drug is metformin. In this study, we identified an endosomal Na ؉ /H ؉ exchanger (NHE) as a new potential target of metformin from an unbiased screen in Caenorhabditis elegans. The same NHE homolog also exists in flies, where it too mediates the effects of metformin. Our results suggest that endosomal NHEs could be a metformin target and provide an insight into a novel mechanism of action of metformin on regulating the endocytic cycle.Diabetes, a common consequence of the growing obesity epidemic, has emerged as a global health threat with over 422 million people worldwide being diagnosed in 2014 (1). Type 2 diabetes mellitus, which is characterized by insulin resistance, is the most common type of diabetes (2).The most prescribed anti-diabetic drug is metformin, 1,1-dimethylbiguanide (3). Metformin reduces glucose production in the liver and increases glucose uptake in muscle and adipose tissue, ameliorating diabetes (4). In addition, metformin exerts beneficial effects on other diseases such as polycystic ovary syndrome, certain cancers, and neurological disorders (2, 5). Several studies identified molecular targets of metformin: it inhibits complex I in mitochondria and decreases NADH oxidation, while reducing proton pumping across the inner mitochondrial membrane and decreasing oxygen consumption rate (6, 7). These effects in turn reduce the proton gradient and increase the AMP/ATP ratio, resulting in activation of AMP-activated protein kinase (AMPK) 2 and triggering a cascade that inhibits gluconeogenic gene expression and energy-consuming processes such as lipogenesis (5, 8). Metformin increases AMP and inhibits adenylate cyclase activity, leading to a reduction in cAMP levels, thereby inhibiting PKA activity and glucagon-dependent glucose production in mice (9). Metformin in physiological doses also suppresses hepatic gluconeogenesis by inhibiting mitochondrial glycerophosphate dehydrogenase (10). Given its versatile effects, it is likely that there are multiple targets of metformin with a wide range of affinities. A better understanding of the targets of metformin will not only allow for a more fine-tuned control of treatment with the drug, but also potentially provide insight into new therapeutic targets for diabetes and other metabolic disorders.Caenorhabditis elegans has been used for studying metabolism, reproduction, aging and other physiological processes, providing useful knowledge of the biology and molecular pathways underpinning human diseases. In this study, we report that metformin reduces C. elegans L1 longevity, a survival span of starvation. Using this phenotype, we performed an unbiased genetic screen and found an endosomal Na ϩ /H ϩ exchanger (NHE) as a potential molecular target of metformin. Moreover, the same NHE homolog in flies also mediates the effects of metformin, suggesting that an NHE could be a conserved target for metformin.

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“…Several genomic and proteomic studies have been carried over the last decade on human and mouse adipose tissue and the outcomes of such efforts were pivotal in gaining insight into the molecular mechanisms underlying obesity and its associated complications [17,18,19,20,21]. A recent proteomics study was carried out on two-major intra-abdominal human fat tissues, namely the subcutaneous and the omental fat to identify and validate obesity-related reference proteins for data standardization [22].…”

Section: Introductionmentioning

confidence: 99%

Proteomics Analysis of Human Obesity Reveals the Epigenetic Factor HDAC4 as a Potential Target for Obesity

et al. 2013

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Sedentary lifestyle and excessive energy intake are prominent contributors to obesity; a major risk factors for the development of insulin resistance, type 2 diabetes and cardiovascular diseases. Elucidating the molecular mechanisms underlying these chronic conditions is of relevant importance as it might lead to the identification of novel anti-obesity targets. The purpose of the current study is to investigate differentially expressed proteins between lean and obese subjects through a shot-gun quantitative proteomics approach using peripheral blood mononuclear cells (PBMCs) extracts as well as potential modulation of those proteins by physical exercise. Using this approach, a total of 47 proteins showed at least 1.5 fold change between lean and obese subjects. In obese, the proteomic profiling before and after 3 months of physical exercise showed differential expression of 38 proteins. Thrombospondin 1 (TSP1) was among the proteins that were upregulated in obese subjects and then decreased by physical exercise. Conversely, the histone deacetylase 4 (HDAC4) was downregulated in obese subjects and then induced by physical exercise. The proteomic data was further validated by qRT-PCR, Western blot and immunohistochemistry in both PBMCs and adipose tissue. We also showed that HDAC4 levels correlated positively with maximum oxygen consumption (VO2 Max) but negatively with body mass index, percent body fat, and the inflammatory chemokine RANTES. In functional assays, our data indicated that ectopic expression of HDAC4 significantly impaired TNF-α-dependent activation of NF-κB, establishing thus a link between HDAC4 and regulation of the immune system. Together, the expression pattern of HDAC4 in obese subjects before and after physical exercise, its correlation with various physical, clinical and metabolic parameters along with its inhibitory effect on NF-κB are suggestive of a protective role of HDAC4 against obesity. HDAC4 could therefore represent a potential therapeutic target for the control and management of obesity and presumably insulin resistance.

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Quantitative Proteomic Analysis of the Adipocyte Plasma Membrane

Cited by 26 publications

References 54 publications

Hypoxia-induced mobilization of NHE6 to the plasma membrane triggers endosome hyperacidification and chemoresistance

Hypoxia-induced mobilization of NHE6 to the plasma membrane triggers endosome hyperacidification and chemoresistance

NHX-5, an Endosomal Na+/H+ Exchanger, Is Associated with Metformin Action

Proteomics Analysis of Human Obesity Reveals the Epigenetic Factor HDAC4 as a Potential Target for Obesity

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